Fan assembly and fan hub cap

ABSTRACT

An apparatus for a fan having an impeller with a hub and a plurality of blades extending from the hub includes a hub cap configured to mount to the hub of the impeller. The hub cap can include a plurality of slots corresponding to the blades of the impeller. The slots are sized to receive the blades when the hub cap is mounted to the hub, which shortens the working length of the blades.

BACKGROUND OF THE INVENTION

Fans used in aviation systems include a case or housing and an impeller contained within the housing to create air flow. A fan is typically designed to meet specific design criteria, which may include alone or in combination any one of at least a particular air flow requirement, pressure rise, and/or rotational speed. When a new design criterion must be met, such as meeting a new air flow requirement, a new fan is designed. An existing fan can be redesigned to meet the new design criteria, such as by altering the impeller size, blade length, number of blades, etc. Often, redesigning the impeller also requires redesigning the fan housing. With any new fan design, costly new production tooling is also needed to then manufacture the fan.

BRIEF DESCRIPTION OF THE INVENTION

A fan assembly includes a fan having an impeller comprising a hub with a diameter and plurality of blades extending radially from the hub, with a distance from the hub to a tip of the blade defining a working length of the blades, and a hub cap configured to mount to the hub. The hub cap includes an end wall having a diameter larger than the diameter of the hub, a peripheral side wall extending from the end wall, and a plurality of slots corresponding to the blades and formed in the side wall. The slots are sized to receive the blades, whereby, when the hub cap is mounted to the hub, the slots receive the blades to effectively shorten the working length of the blades.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fan assembly;

FIG. 2 is a partial cross-section view of the fan assembly from FIG. 1;

FIG. 3 is a top view of an impeller from the fan assembly from FIG. 1;

FIG. 4 is a side view of the impeller from FIG. 3;

FIG. 5 is a top view of a hub cap useable with the fan assembly from FIG. 1;

FIG. 6 is a side view of the hub cap from FIG. 5;

FIG. 7 is a top view of the assembled impeller and hub cap from FIGS. 3 and 5;

FIG. 8 is a side view of the assembled impeller and hub cap from FIGS. 4 and 6; and

FIG. 9 is a graph showing several fan performance curves for the fan assembly from FIG. 1 with and without the hub cap.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of a fan assembly 10. The fan assembly 10 includes a fan 12 and a hub cap 14 configured to selectively mount to the fan 12, as described below. The fan 12 includes an impeller 16 having a hub 18 with a plurality of blades 20 extending radially from the hub 18. The fan 12 further includes a fan housing 22 which receives the impeller 16. The fan 12 is shown herein as an axial fan that increases the pressure of air flowing through it; this fan 12 is illustrated for exemplary purposes only, and the hub cap 14 can be configured for use with a wide variety of fans. The fan assembly 10 can function to create air flow without or without the hub cap 14.

FIG. 2 is a partial cross-section view of the fan assembly 10 from FIG. 1. The fan assembly 10 further includes a motor 24 coupled to the impeller 16 via an output shaft or drive shaft 26. The hub 18 of the impeller 16 includes a bore 28 through which the drive shaft 26 extends. A fastener 30 couples the impeller 16 to the drive shaft 26, one non-limiting example of which includes a threaded fastener or screw. Other fastening methods can also be used to attach the impeller 16 to the drive shaft 26, including other mechanical fasteners or an adhesive or bonding agent. In one arrangement, the fastener 30 can be a nut which engages the drive shaft 26.

The fan housing 22 is shown herein as having a generally cylindrical side wall 32, with an inlet end 34 and an outlet end 36, both of which are open to permit the flow of air through the fan housing 22. The impeller 16 is positioned at the inlet end 34 to draw air into the fan housing 22.

FIGS. 3 and 4 are top and side views, respectively, of the impeller 16. The hub 18 includes an end wall 38 and a peripheral side wall 40 extending from the end wall 38. The side wall 40 of the hub 18 further has a peripheral edge 42 opposite the end wall 38.

An opening 44 to the bore 28 is formed in the end wall 38. More specifically, as shown herein, the end wall 38 can have a recess 46 in which the opening 44 to the bore 28 is located. The recess 46 and opening 44 can be coaxially aligned along the rotational axis of the impeller 16.

The plurality of blades 20 extend radially outwardly from the side wall 40, from proximal ends 48 which join the side wall 40 to free distal ends 50. The number, spacing, geometry (including length, pitch, etc.) of the blades 20 can vary from the configuration shown herein.

A working length L of the blades 20 is generally defined by the length of the blades 20 exposed to air flow. Here, without the hub cap 14 (FIG. 1), the working length of each blade 20 is the distance from the proximal end 48 to the distal end 50.

FIGS. 5 and 6 are top and side views, respectively, of the hub cap 14. The hub cap 14 includes an end wall 52 and a peripheral side wall 54 extending from the end wall 52. The side wall 54 of the hub cap 14 further has a peripheral edge 56 opposite the end wall 52 that defines an open back of the hub cap 14. The hub cap 14 can, for example, be made of metal, a composite material, or other suitable materials.

An opening 58 is formed in the end wall 52. More specifically, as shown herein, the end wall 52 can have a recess 60 in which the opening 58 is located. The recess 46 and opening 44 can be coaxially aligned along the rotational axis of the impeller 16.

A plurality of slots 62 are formed in the side wall 54. The slots 62 can extend from the peripheral edge 56 toward the end wall 52. As shown herein, each slot 62 can include two opposing sides 64 which extend from an open end 66 at the peripheral edge 56 to a closed end 68. The number, spacing, geometry (including length, pitch, etc.) of the slots 62 can vary from the configuration shown herein.

FIGS. 7 and 8 are top and side views of the assembled hub cap 14 and impeller 16. The hub cap 14 is received over the hub 18 of the impeller 16, with blades 20 received by the slots 62. The opening 58 of the hub cap 14 is coaxially aligned with the opening 44 of the hub 18, and the hub cap 14 is secured to the drive shaft 26 using the same fastener 30 that is used for the impeller 16 (see FIG. 2). Other fastening methods can also be used to attach the hub cap 14 to the impeller 16, including other mechanical fasteners or an adhesive or bonding agent.

The recess 60 of the hub cap 14 can be dimensioned to nest within the recess 46 of the hub 18, and the end walls 38, 52 and side walls 40, 54 of the hub cap 14 and hub 18 substantially align with each other so as to limit how far the hub cap 14 extends beyond the hub 18. By minimizing the dimensions of the hub cap 14 with respect to the dimensions of the hub 18, the hub cap 14 can be used with an existing fan 12 without modifying the fan housing 22.

The slots correspond in number and size to the blades, such that the slots receive the blades when the hub cap 14 is mounted to the impeller 16. The pitch and shape of the blades 20 may require the hub cap 14 to be rotated or twisted as the slots move over the changing shape of the blades 20 to the full seated position on the impeller shown in FIGS. 7-8.

As noted above, the working length L of the blades 20 is generally defined by the length of the blades 20 exposed to air flow. Here, with the hub cap 14 assembled with the impeller 16, the working length L of each blade 20 is the distance from the peripheral side wall 54 of the hub cap 14 to the distal end 50 of the blade 20. The hub cap 14 thereby shortens the effective length (or span) of each blade 20 and thus alters the performance characteristics of the fan 12. Conversely, the hub cap 14 also effectively enlarges the working hub of the fan 12.

FIG. 9 is a graph of several fan performance curves in terms of fan airflow rate (expressed in units of cubic feet per minute or CFM) and pressure rise (expressed in units of inch of water gauge or in. wg). The graph includes performance curves for the fan assembly 10 with and without the hub cap 14. It is noted that the various fan performance curves are shown for illustrative purposes only; the performance of the fan assembly 10 shown herein may differ from the performance curves shown in FIG. 9 without departing from the embodiment of the invention discussed herein.

Line A is the performance curve for the fan assembly 10 without the hub cap 14 which meets a first design point X of a particular combination of airflow rate and pressure rise. Under some circumstances, such as for another application of the fan assembly 10, a second or new design point Y of a different combination of airflow rate and pressure rise may be required. In some cases, the fan assembly 10 may be able to meet the new design point Y by adjusting the rotational speed of the impeller 16. However, in the illustrated case, lowering the rotational speed does not result in a performance curve that meets the new design point Y. Line B is the performance curve for the fan assembly 10 at approximately 90% of the rotational speed for Line A and Line C is the performance curve for the fan assembly 10 at approximately 75% of the rotational speed for Line A, neither of which passes through the new design point Y.

Line D is the performance curve for the fan assembly 10 with the hub cap 14 mounted on the impeller 16 as shown in FIGS. 7-8. By adding the hub cap 14, and in this particular case without adjusting the rotational speed of the impeller 16, the fan assembly meets the new design point Y. Adding the hub cap 14 effectively enlarges the working hub of the fan assembly 10 or conversely, shortens the working length L of the blades 20 for the given blade diameter, so that the new design point Y can be met. Instead of making an entirely new impeller with a larger hub and shorter blades, the hub cap 14 can be used.

It is noted that while the first and second design points X, Y shown in FIG. 9 have approximately the same pressure rise requirements, any combination of airflow rate and pressure rise may be required. It is also noted that while the fan assembly 10 with the hub cap 14 mounted on the impeller 16 as shown in FIGS. 7-8 can meet the new design point Y without adjusting rotational speed, in some cases and for some design criteria, a combination of the hub cap 14 and a rotational speed change may be required.

The above described embodiments provide for a variety of benefits, including that the hub cap can be added to an existing fan in order to effectively alter the impeller configuration so that the fan can meet other performance requirements in addition to those intended with the original design of the fan. Fans can be benefited by aspects of the invention discussed herein by allowing for performance changes without requiring a new impeller; in one example, a fan with a relatively small hub diameter and relatively long blades can be provided with the hub cap in order to create a fan with a larger hub diameter and shorter blades. The hub cap does not require any special attachment or assembly since it can be secured to the existing impeller drive shaft, using the existing fastener. Rather than custom-designing a new impeller, which would otherwise be required, this apparatus and method can save time and costs in only manufacturing a new hub cap for the fan.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A fan assembly comprising: a fan having an impeller comprising a hub with a diameter and a plurality of blades extending radially from the hub, with a distance from the hub to a tip of the blade defining a working length of the blades; and a hub cap configured to mount to the hub, comprising: an end wall having a diameter larger than the diameter of the hub; a peripheral side wall extending from the end wall; and a plurality of slots corresponding to the blades and formed in the side wall; wherein the slots are sized to receive the blades, whereby, when the hub cap is mounted to the hub, the slots receive the blades to effectively shorten the working length of the blades.
 2. The fan assembly of claim 1 wherein the fan further comprises a motor having an output shaft, wherein the impeller is mounted to the output shaft by a fastener.
 3. The fan assembly of claim 2, wherein the end wall of the hub cap comprises an opening which receives the fastener.
 4. The fan assembly of claim 3, wherein the end wall of the hub cap comprises a recess, and the opening is located in the recess.
 5. The fan assembly of claim 1, wherein the hub cap is mechanically fixed to the hub.
 6. The fan assembly of claim 1, wherein the hub cap is bonded to the hub.
 7. The fan assembly of claim 1 wherein the fan further comprises a fan housing, wherein the impeller and the hub cap are located within the fan housing.
 8. The fan assembly of claim 1, wherein the plurality of blades extend radially from the hub to distal ends, and a distance between the peripheral side wall of the hub and the distal ends of the blades defines the working length of the blades.
 9. The fan assembly of claim 1, wherein the plurality of slots are angled to correspond to a pitch of the plurality of blades where the plurality of blades meet the peripheral side wall of the hub cap.
 10. The fan assembly of claim 9, wherein the plurality of blades extend radially from the hub to distal ends, and the pitch of the plurality of blades changes between the hub and the distal ends.
 11. The fan assembly of claim 1, wherein the peripheral side wall of the hub cap comprises a peripheral edge opposite the end wall, wherein the plurality of slots extend from the peripheral edge toward the end wall.
 12. The fan assembly of claim 1, wherein the hub of the impeller comprises an end wall having a diameter smaller than the diameter of the end wall of the hub cap, and a peripheral side wall extending from the end wall of the hub.
 13. The fan assembly of claim 1, wherein the peripheral side wall of the hub extends substantially parallel to the peripheral side wall of the hub cap. 